fix tracer configuration merging

[tsloughter]

Ran into this while working on some examples for docs.

This patch also makes the default exporter be undefined. I'm not sure what the best is here, when its defaulting to OTLP it crashes bad (confusing). So maybe it should instead be stdout or OTLP but handle the crash better to log a message to let the user it tried using OTLP but something wasn't configured or available.

[ferd]

Approved the changeset on intent. All tests failing is necessary to fix first.

That being said, the idea of setting OTLP and getting crash logs explaining what is missing in the config would likely be best for someone wanting it to work in most cases, assuming their intent is ultimately to have that exporter going. For the purposes of docs, would having a "demo" stdout exporter make sense to configure rather than defaulting to nothing?

[tsloughter]

Ugh, its the libwxgtk actions change I saw someone mention on twitter.

[tsloughter]

https://twitter.com/my_olive_tree/status/1369526310448607234

@puzza007 do you know the fix?

[tsloughter]

Woops, pinged Erlanger Paul Oliver instead of Erlanger @paulo-ferraz-oliveira :)

[tsloughter]

Aggh, erlef/setup-elixir is also broken but because of libcrypto.

[codecov]

Codecov Report

Merging #221 (dd2620c) into main (ff12ebb) will decrease coverage by 0.12%.
The diff coverage is 16.66%.

@@            Coverage Diff             @@
##             main     #221      +/-   ##
==========================================
- Coverage   34.96%   34.84%   -0.13%     
==========================================
  Files          37       37              
  Lines        3037     3045       +8     
==========================================
- Hits         1062     1061       -1     
- Misses       1975     1984       +9     

Flag	Coverage Δ
api	61.11% <ø> (ø)
elixir	18.05% <ø> (ø)
erlang	34.69% <16.66%> (-0.13%)	⬇️
exporter	19.54% <ø> (ø)
sdk	77.47% <16.66%> (-1.34%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
apps/opentelemetry/src/opentelemetry_sup.erl	100.00% <ø> (ø)
apps/opentelemetry/src/otel_batch_processor.erl	67.34% <9.09%> (-7.66%)	⬇️
apps/opentelemetry/src/otel_configuration.erl	79.71% <100.00%> (+1.76%)	⬆️

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[tsloughter]

So I've updated it to have some useful warning logs if the exporter fails to initialize.

I'm still unsure if we should default to OTLP exporter or something like stdout. Defaulting to the OTLP exporter, which has default host and port does make for simpler configuration in demos/guides when exporting to a local collector, but maybe that is actually worse since most people in prod will not have the collector on localhost.

[paulo-ferraz-oliveira]

Yeah, for the libwx stuff I just "downgraded" to ubuntu-18.04. I'm not sure if it's solved in gleam-lang/setup-erlang, at the moment. But I believe I tried the latest version and other issues arose. Ah, yeah, it was the fetching of versions from Erlang Solutions that aren't there.

[puzza007]

Woops, pinged Erlanger Paul Oliver instead of Erlanger @paulo-ferraz-oliveira :)